Reproduction

Maturity

Male perch mature earlier than the females, normally between the ages of 2-4 years. However under exceptional circumstances, when food is abundant, maturity can be reached in as little as one year. Females grow faster than the males but take longer to mature, normally at around 3-5 years. Perch are sexually dimorphic, the females growing larger than the males.

Spawning

Spawning lakes place over a two to three week period during the spring and can commence any time from March to May depending on weather conditions but usually occurs when water temperatures have reached about 9 or 10ºc.

Male perch gather first in favoured areas i.e., quiet backwaters, shallow bays, etc., in water of 1-2 metres deep. The females arrive soon after. Several males will accompany each female, swimming with her through aquatic vegetation, reeds, or submerged branches until ovulation occurs. The eggs are cast in long sticky glutinous ribbons a metre or more in length and are drawn from the body of the female as she swims forward through the obstacles. The eggs are then fertilised by two or more attendant males.

Fish are very prolific; the number of eggs carried by the female (referred to as her fecundity) in some cases being enormous. The number however is variable and dependant on her condition and her size. Generally speaking the larger the female the greater the number of eggs she will carry. This can be anything from 3,000 in a small female to 210,000 in one of the larger specimens in the 3lb to 4lb range! But it must be remembered that only a small percentage of this vast number will survive to become adult perch.

Eggs

The perch, like most coarse fish, lays demersal eggs which are about 1.0-2.5mm in diameter. Perch eggs hatch in 8-10 days depending on weather conditions. Light is considered important for ripening of the eggs but the most vital factor is temperature. Fluctuations in temperature may advance or retard the hatching process. Fortunately water retains its heat much longer than air, so the eggs can survive sudden cold snaps provided they are of short duration.

Hatching

When hatched each of the tiny fish, or Alevins as they are known at this stage, is equipped with a yolk sac, the contents of which will provide its only source of food for the next 10-20 days or until the Alevin is able to feed for itself on the tiny animal organisms (Zooplankton) which inhabit the water.

Survival and growth of the Alevin is dependent on habitat type and the availability of suitable food organisms. Temperature once again plays a critical role, as water temperatures control the development and abundance of zooplankton. Perch are totally dependent on zooplankton as a food source in their first year of life.

Key facts:

Age of sexual maturity- 2 to 4 years for males- 3 to 5 years for females

Spawning time - March to May

Spawning water temperature - 9 to 10°C

Number of eggs produced- ~3,000 from a small female- ~210,000 from a large female

Egg size - 1.0 to 2.5 mm

Time to hatch - 8 to 10 days

A female perch spawning

Perch eggs

Perch fry

A shoal of young perch

Hatching (continued)

High water temperatures will speed up the rate at which the yolk sac is absorbed and low temperatures will slow it down. The tiny perch are now about 6mm long. During this time the Alevins remain attached to the object on which they hatched. If they didn’t, they would fall to the bottom and could suffocate in the silt. Once they are strong enough to swim for themselves the Alevins must make the perilous journey to the surface to take in atmospheric air to inflate their swim bladders. If the surface is covered by detergent diesel from boats or any other pollutant then they cannot complete this task and thousands of fry may perish.

Fry development

At this stage of their development the dominant food items eaten by the larval perch are:

Rotifers - weird and wonderful microscopic creatures of which over 500 species exist in British waters.

Copepods - tiny crustaceans with one of the most numerous being the Cyclops.

Cladocerans - the most well-known member of this group being the water fleas Daphnia.

As the perch grow and develop, larger food items will be consumed avidly. Any animal organism that the tiny perch can fit into its mouth will be eaten. These are mainly benthic (bottom dwelling) creatures such as bloodworms, midge pupae, the water louse Asellus, freshwater shrimps Gammarus and a host of insect nymphs and larvae.
Eventually the perch become piscivorous eating a wide variety of small fish. Feeding in perch develops into a diurnal pattern, with maximum activity at dawn and dusk periods.

The fight for survival

Perch can live for over 20 years and from the moment they are laid the perils they face are many. Large numbers of eggs are consumed accidentally by weed eating birds such as swans and coots. Some may be swept away in spring floods or lost through pollution. Once hatched the tiny fry are at the mercy of the elements and may die of cold or starvation. Predators also take their toll. Baby pike born earlier than the perch, prey heavily on the hatchlings as do the larvae of various insects such as the Dytiscus beetle and the voracious dragonflies. Cannibalism in perch is also common – the older year classes preying upon the younger, especially if other food sources are unavailable.
There are also eels, trout, grass snakes, otters, herons, grebes, cormorants and many, many more creatures hunting the perch throughout its life. Other hazards faced are parasites and diseases of one kind or another – in fact it’s a wonder that the perch manages to survive all this at all but survive it does!

So the next time you catch a perch, no matter what its size, appreciate its beauty and think about what it has experienced in its struggle to live. Treat your prize with respect and handle it with care (see Handling perch for more advice). If you are fortunate to catch a specimen of two pounds or more then you are indeed a lucky person – so treat her with care and gently slip her back. Because she has made it……..Against All Odds.